I thought the same thing. However I tried something different...I enabled LFS to show the pedals on the bottom right, and I enabled auto-clutch.
With racing setups, the car with auto-clutch seemed to set off perfect with just a light press on the throttle, and observing the pedal bars, LFS seemed to be using the clutch as you would in a real car. However when I tried to do it manually, it took some real precise movements, and it did stall and shake alot.
I am wondering myself if it has something to do with the clutch and throttle being on the same level on my G25, whereas the throttle is set further back than the clutch in real life.